LEPIDOGANOIDEI 131 



red sandstone, and are as follows : — Cheiraeanthus, with a 

 single dorsal situated in front of the anal; Acantlwdes, in 

 which the dorsal is situated behind the anal ; and Dipla- 

 canthus (fig. 48), in which there are two dorsals. 



The Diplacanthus striatus is found in the " old red" of 

 Cromarty. In fig. -48, as in the other figures, p is the pectoral 

 fin, d the dorsal, v the ventral, a the anal, and c the caudal. 

 In this species the upper lobe of the caudal is much prolonged. 

 The fin-spines in the Acanthodii were, like those of the recent 

 dog-fish (Sjoinctx), simply imbedded in the flesh, with their 

 base, as it were, unfinished ; not provided, as in the Siluroids 

 and other modern bony fishes, with a joint-structure. 



Chcirolqris, with the minute scales of the family, has the 

 dorsal behind the anal, but has no spine in any fin : the 

 mouth is large, the teeth small and uniserial. Some species 

 of the present family, Acantlwdes Bronnii, Ac. sulcatus, existed 

 in the seas of the carboniferous period. 



Family III. — Ccelacanthi. 



The species of this family are characterized by the hollow- 

 ness of the rays or spines ; whence the name. The caudal fin 

 has a peculiar structure, the vertebral column being continued 

 into and beyond its middle part, supporting a kind of slender 

 appendage between the two normal lobes. The species of the 

 genus are most abundant in the Devonian and carboniferous 

 formations ; but some occur in oolitic and even, if Macropoma 

 be a true Ccelacanth, in cretaceous 

 beds ; but all became extinct before 

 the tertiary epoch. 



GlyptoUpis had a heterocercal tail, 

 with rounded scales, smooth exter- 



Fig. 49. 



nally, and with radiating compart- GlyptoUpis microlepidotus 

 ments internally. The G. microle- (Devonian). 



pidotus, of which a magnified view of the inner side of some 



